Two New Tanzanian Acanthaceae

Abstract

Summary. Two recently discovered species, Crossandra leucodonta and Stenandrium grandiflorum, are described, and their relationship with the other species of the two genera discussed. Since the revisions of African Crossandra (Vollesen 1990) and Stenandrium (Vollesen 1992) collecting in the floristically very rich and to a large extent very poorly known Udzungwa Mts in southern Tanzania has resulted in the discovery of two new species. Crossandra leucodonta Vollesen, sp. nov. C. tridentatae atque C. friesiorum affinis sed bracteis in dimidio apicali albis, in dimidio inferiore tantum viridibus nec per totam longitudinem viridibus differt. Ab eis atque ab omnibus ceteris speciebus africanis Crossandrae sepalo dorsali uninervato tantum et ad apicem attenuato longe aristato, nec e basin binervato neque ad apicem bidentato differt. Typus: Tanzania, FrimodtMoller et al. NG092 (K, holotypus; C, isotypus). Perennial herb, basal part of stems creeping and rooting (eventually dying away from the back), apical part erect, to 15 cm tall; young stems not conspicuously swollen below nodes, sericeous-tomentose with long curly many-celled hairs. Leaves opposite or in pseudo-whorls of 4, dark green above, paler beneath, sparsely sericeouspubescent with many-celled curly hairs along veins beneath, above with scattered hairs on veins and lamina; petiole 0.5 - 1.5 cm long; lamina gradually narrowed below middle, ovate to elliptic, largest 4 - 6 x 2 - 2.5 cm; apex subacute to acuminate, with a more or less well-defined tip; base attenuate decurrent; margin slightly crenate; with 3 - 5 main lateral veins each side. Spikes 1 - 2 cm long, with 2 pairs of sterile bracts at base; peduncle 1.5 - 3.5 cm long, sericeous-tomentose with long many-celled curly hairs. Fertile bracts obovate in outline, dark green with white lobes, 14 - 18 x 5 - 6 mm, basal part with scattered long many-celled curly hairs, apical part of lobes finely puberulous, deeply 3-lobed and lower down also with a single tooth per side, lobes 7 9 x 1 - 2 mm, narrowly triangular, tapering gradually to an acuminate tip. Bracteoles 3 -5 mm long, linear-lanceolate, with a long cuspidate tip, with indumentum as bracts. Sepals glabrous, dorsal 8 - 9 mm long, elliptic with a long cuspidate awn-like tip, 1veined from base, ventral c. 7 mm long, oblong, acuminate, lateral c. 5 mm long, lanceolate. Corolla white or with a faint pale lilac tinge to limb; tube c. 10 mm long; limb c. 9 mm long. Capsule and seed not seen.